Octahedral cobalt(III) complexes in dipolar aprotic solvents. XIII. The isomerization of cis- and trans-Dibromobis(ethylenediamine)cobalt(III) ions, [CoBr₂ em₂]⁺, in anhydrous sulpholane

Abstract

The isomerization of cis- and trans-[CoBr₂ en₂]⁺ has been studied in anhydrous sulpholane (tetramethylene sulphone). No evidence has been found for the presence of species containing coordinated solvent molecules, and the mechanism of isomerization of both isomers is interpreted as S_Nl the rates being influenced by ion-pair formation. Activation parameters have been measured for the isomerization of both species at various bromide concentrations. Equilibrium constants and standard state entropy and enthalpy changes for the isomerization reaction and for the formation of the cis-[CoBr₂ en₂]^{+ .......}Br- ion pair have been measured.